As an adult hematologist, Stephanie Perry has worked in the Hemostasis and Thrombosis Clinic at Duke University Medical Center for three years as a fellow, and this past year as a faculty member. During this time, she has seen many hemodialysis patients with recurrent vascular access thrombosis. Most of these patients have laboratory evidence for being hypercoagulable. However, the best pharmacplogic prevention for vascular access thrombosis in hemodialyis patients is not known. Dr. Perry's career goal is to become an independent clinical investigator. Her desire is to be able to design studies based on clinical questions that arise from the patient care setting. To attain her goal, Dr. Perry will work under the mentorship of Dr. Ortel who is Director of the Hemostasis and Thrombosis Center, Dr. Becker, MD who is Director of the Cardiovascular Thrombosis Center, and Dr. Greenberg who is Director of the Durham DaVita Dialysis Centers. She will have collaborators at the Duke Clinical Research Instittute who will provide her the skills necessary to become an expert in designing and analyzing clinical studies. Dr. Perry will also take structured courses which will supplement her master's degree in clinical research. The proposed research project will be to perform a pilot, randomized clinical trial using the antithrombotic agent dalteparin during hemodialysis days and non-hemodialysis days for the first 3 months after new arteriovenous graft placement. The specific aims include the following: 1) asess the safety and efficiacy of dalteparin in prevention of recurrent vascular access thrombosis;2) determine the pharmacokinetics of dalteparin in hemodialysis patients;and 3) evaluate changes in biomarkers important in inflammation, coagulation, and growth factors at specific times during prophylatic dalteparin administration. The design of this proposal will establish a model in which to evaluate for pharmacologic prevention of recurrent thrombosis. The methods will allow for the special monitoring of anticoagulant effect by testing anti-factor Xa activity in order to avoid bioaccumulation in hemodialysis patients. This proposal will also evaluate biomarkers which may help in developing a risk assessment model to identify patients at greatest risk. Relevance: Patients must have vascular access for hemodialysis. Access complications account for 16- 25% of the hospital admissions for these patients, therefore contributing to both morbidity and health costs.